The present invention relates to a magnetic disc apparatus and a magnetic disc.
Heretofore, magnetic disc apparatus tend to reduce a spacing between a flying head slider and a magnetic disc in order to realize a high density recording. Also, magnetic disc apparatus tend to rotate a disc rotating spindle at high speed in order to shorten an information transfer time. Concurrently therewith, if floating dust existing within the magnetic disc apparatus and powders produced when assembly parts composing the magnetic disc apparatus are worn enter into the spacing between a lifting force generating surface of a slider rail of the flying head slider and the magnetic disc, recorded information can not be read out temporarily. Also, if the surface of the slider rail is smudged with dust and oily mists, the flying head slider can not skim stably. There is then the increasing risk that the magnetic disc apparatus will be damaged by a destructive sliding accident.
Recently, the spacing between the flying head slider and the magnetic disc is reduced more. There is then another problem that a so-called head crash is caused even by gas generated from parts of the magnetic disc apparatus. Silicon rubber packings that had been used so far to hermetically seal the magnetic disc apparatus contain large amounts of siloxane which is instantaneously chemically changed to hard silicon oxide by heating. The concentration of siloxane gas increases as a temperature within the magnetic disc apparatus rises. The moment the flying head slider and the magnetic disc contact with each other, the heat is generated from friction. This frictional heat has energy sufficient to promote a chemical change from siloxane to silicon oxide. When the silicon oxide is generated by the contact between the flying head slider and the magnetic disc, there lies a hard substance (i.e., silicon oxide) between the flying head slider and the magnetic disc with the result that a destructive head crash occurs. To solve this problem, in Japanese laid-open patent publication No. 4-132072 the silicon rubber that had been so far employed as the packing of the magnetic disc apparatus is replaced with a fluoro rubber which generates less siloxane gas.
If the packing of the magnetic disc apparatus is made of the fluoro rubber instead of the silicon rubber, then it becomes possible to effectively suppress the siloxane gas from being generated within the magnetic disc apparatus. Further, if the magnetic disc apparatus incorporates a gas adsorbent, then it becomes possible to effectively remove siloxane gas generated from the inside of the magnetic disc apparatus and/or entered into the magnetic disc apparatus from the outside. However, in as much as the magnetic disc apparatus is miniaturized progressively, the magnetic disc apparatus cannot provide a sufficient space for incorporating a sufficient amount of gas adsorbent. Furthermore, to make the magnetic disc apparatus high in reliability, it is important and desirable to prevent the head crash from taking place even when the siloxane gas exists within the magnetic disc apparatus.